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Bretschneider's formula

Revision as of 10:03, 2 December 2006 by JBL (talk | contribs) (Do not copy from Wikipedia)

Suppose we have a quadrilateral with edges of length $a,b,c,d$ (in that order) and diagonals of length $p, q$. Bretschneider's formula states that the area $[ABCD]=\frac{1}{4}*\sqrt{4p^2q^2-(b^2+d^2-a^2-c^2)^2}$.

It can be derived with vector geometry.

The Proof

See Also

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